Planar slot antenna grid

ABSTRACT

A planar slot antenna grid contains a number of waveguide-slot radiators having wide reverse side and wide outer side faces in which there are obtained, respectively, exciting slots of coupling and radiating slots. The faces lie correspondingly in two parallel planes, and a waveguide-feeder network is formed by waveguide distributors of power and feeding waveguides. Channels of the waveguides communicate with the exciting slots of coupling. The waveguide-slot radiators represent strip-line waveguides including a common dielectric substrate. The reverse side of the substrate is covered by a metallized coating serving as a common wide reverse side face of the waveguide-slot radiators. Each wide outer side face of the radiators represents a strip-line made of alternating narrow and wide segments formed on the outer side face of the dielectric substrate.

FIELD OF INVENTION

This invention relates to radio engineering, microwave technologyantenna-feeder devices, and, more specifically, to a planar slot antennagrid.

PRIOR ART

Work is currently under way on creating antennas of microwave designwhich would be compatible with modern radio-electronic equipment andensure an efficiency factor above 0.7 at apertures lying within 15 to 30wave lengths in free space, and at a working frequencies range of notless than 10%. Apart from that, these antennas should be simple inconstruction and have small mass/weight and thickness. They should havehigh manufacturabilty and replication or recurrence of dimensions orparameters.

Attempts to make antennas with said characteristics have materialized inthe creation of a slot antenna grid of a printed circuit design("Radio-Electronics Abroad", Summary, Publication 7(39), 1989 [SRIER,Moscow, "Planar Antennas for Direct TV Broadcasting Systems", pp. 3, 4,FIG. 1]). This slot antenna grid contains a dielectric substrate withwide slot-windows communicating with a waveguide-feeder network formedby strip-lines.

Since the slot antenna grid is obtained in its printed circuit design,it is adaptable to streamlined manufacture, is simple in construction,has small mass/weight and thickness, and high replication of dimensionsand parameters.

However, the antenna grid exhibits comparatively big losses in thewaveguide-feed network, and both at an aperture size lying within 15 to30 wave lengths in free space and at working frequencies range of notless than 10%, its efficiency factor does not exceed 0.6. This isconditioned by the fact that the waveguide-feeder network of thisantenna grid is produced on strip-lines exhibiting losses within therange of 0.05 to 0.1 d.b./cm.

Known in the prior art also is a waveguide-slot antenna grid on hollowor cored waveguides (D. I. Voskresenski et al. "Antennas & MicrowaveDevices.Designing Phased Antenna Grids", 1981, Radio and Communication,Moscow, pp. 126-128). In this antenna grid, waveguide-slot radiators andwaveguide-feeder network are obtained on hollow metallic waveguides.

Under the above conditions, the slot antenna grid of this kind providesa high efficiency factor which is due to the fact that the losses in thewaveguide-slot radiators and the waveguides of the waveguide-feedernetwork are minimal and do not exceed 0.001 d.g./cm.

Such construction of the antenna grid is, however, not easilymanufacturable because its manufacturing involves a lot of unprogresivemechanical assemblage which does not provide required replication ofdimensions and parameters of the antenna grid. Apart from that, theemployment of hollow metallic waveguides results in that this antennagrid has large mass/weight and thickness, and a high level of metalconsumption.

Known in the prior art is also a slot antenna grid ("Radio-ElectronicsAbroad", Summary, Publication 2(34), 1989, [SRIER, "PlanarWaveguide-Slot Antenna Grids", pp. 24-26, FIG. 2]), containing a numberof waveguide-slot antenna radiators having wide reverse and outer sidefaces in which there are obtained, respectively, exciting slots ofcoupling and radiating slots. The faces lie correspondingly in twoparallel planes, and a waveguide-feeder network containing waveguidedistributors of power and feeding waveguides is also obtained channelsof which are communicating with the exciting slots of coupling.

Every waveguide-slot radiator is formed as a result of plate assemblymanufactured from a metal sheet with radiating slots obtained in it. Theplate representing a wide outer side face of this radiator has a base inwhich, under the waveguide of each waveguide-slot radiator, arectangular groove is obtained with formation of two narrow side facesand one wide reverse side face of this waveguide-slot radiator. Thewaveguide-feeder network is made on hollow metallic waveguides.

Under above conditions, such a planar slot antenna grid demonstrateshigh efficiency factor owing to the fact that the losses in thewaveguides of the waveguide-slot radiators and the waveguides of thewaveguide-feeder network are minimal.

In practice, however, the manufacturing of such planar slot antennagrids reveals that its construction is complex, and the manufacturing ofthis antenna grid is labour consuming and not easily adaptable becauseit involves a lot of unprogressive mechanical assemblage which does notprovide a high level of replication of dimensions and parameters of thisantenna grid. Apart from that, in the process of making thewaveguide-slot radiators, it is difficult to test or run a check on aninternal seam or joint between the ribs of the narrow side faces of thewaveguides obtained at the base, and the metal sheet with radiatingslots. The presence of even a short segment which is not caulked bysoldering, in these joints, results in spurious or stray couplingbetween the adjacent waveguide-slot radiators and, consequently, reducesa gain factor of the antenna grid. In other words, the construction ofthe present planar slot antenna grid is unreliable. Apart from that,such an antenna grid has greater mass/weight and thickness than that ofthe antenna grids produced according to the printed circuit design.Mainly, this is conditioned by the fact that the construction of thepresent grid employs the metallic base under the waveguides of thewaveguide-slot radiators, the base having greater mass/weight andthickness. The employment of the waveguide-feeder network on the hollowmetallic waveguides is responsible for, even greater increase inmass/weight and thickness of this antenna grid.

SUMMARY OF THE INVENTION

The invention addresses the problem of creating a planar slot antennagrid in which, owing to constructive design modifications of thewaveguide-slot radiators, while maintaining a high efficiency factorwithin a wide range of frequencies, simplicity and reliability ofconstruction, as well as smaller thickness and weight, and highermanufacturabilty of this antenna grid, are ensured.

This problem is solved, in a planar slot antenna grid containing anumber of waveguide-slot radiators having wide reverse side and outerside faces, in which there are obtained, respectively, exciting slots ofcoupling and radiating slots, by having the faces lying correspondinglyin two parallel planes. A waveguide-feeder network contains waveguidedistributors of power and feeding waveguides, channels of whichcommunicate with the exciting slots of coupling. According to theinvention, the waveguide-slot radiators represent strip-line waveguidescomprising a common dielectric substrate, the reverse side of which iscovered by metallized coating serving as a common wide reverse side faceof the waveguide-slot radiators, each outer side face of whichrepresenting a strip line made of alternating wide and narrow segmentsformed on outer side face of the dielectric substrate.

Construction of the waveguide-slot radiators is designed essentially asthe printed circuit dielectric substrate. On one side, there is placed anumber of wide outer side faces of the printed circuit strip-linewaveguide-slot radiators in the form of strip-lines of alternating wideand narrow segments, and on the other side, there is obtained a commonwide reverse side face of these strip-line waveguide-slot radiators inthe form of metallized coating.

Construction of such an antenna grid offers the possibility tomanufacture waveguide-slot radiators of the printed circuit design. Inother words, the construction permits one to abandon a lot of mechanicalassemblage and to introduce progressive methods of the printed circuittechnology, specifically, by means of photolithography. This makes theantenna grid adaptable to streamlined manufacture with reduced labourconsumption.

Apart from that, the employment of printed circuit technology in makingthe antenna grid allows a high level of replication of dimensions andparameters of the antenna grid to be obtained.

Construction of the present planar slot antenna grid provides for theexecution of the waveguide-slot radiators as a single unit member, i.e.the dielectric plate with wide outer side faces of the printed circuitwaveguide-slot radiators on the one side and a thin metallized coatingon the other side. Thickness and mass/weight of such a member are small,and its construction is simple and reliable. The antenna grid also hassmall mass/weight and thickness, and its construction is simple andreliable.

The proposed planar slot antenna grid reveals a high, above 0.7,efficiency factor at apertures lying within 15 to 30 wave lengths infree space, and at working frequencies of not less than 10%. This isconditioned by the fact that the waveguide-slot radiators of thisantenna grid are produced on the strip-line waveguides representingbasically the waveguides of rectangular section filled in with thedielectric material of which the substrate is made. Losses in such stripline waveguides are within 0.02 to 0.03 d.g./cm, which does notsubstantially reduce the efficiency factor of the antenna grid.

It is advisable to place the waveguide-feeder network and on themetallized coating which represents a common wide side face of thefeeding waveguides and the waveguide distributors of power.

Thus, it becomes possible to simultaneously use the metallized coatingof the substrate both as wide reverse side faces of the strip-linewaveguide-slot radiators and as one of the wide side faces of thewaveguides of the waveguide-feeder network. This, in turn, permits to areduction in thickness and mass/weight of the antenna grid.

Similarly, it is advisable that the waveguide-feeder network has a basein which there are obtained rectangular grooves having surfaces which,together with the metallized coating surface, would create channels ofthe waveguide-feeder network.

This construction makes it possible to obtain, after the radiatorsubstrate is assembled with the base of the waveguide-feeder network,the waveguides of rectangular section on which the feeding waveguidesand the waveguide distributors of power in the form of, for example,H-tee are easily realized. This offers the possibility of making allwaveguides of the waveguide-feeder network lie in one plane, and reducesa thickness of the antenna grid.

It is recommended that longitudinal axes of the strip-line wave-guidesare parallel to each other, that a distance between longitudinal axes ofthe adjacent strip-line waveguides be less than a wave length in freespace at higher frequency, and that the distance be more than 1/20 valueof this wave length with lateral width of the wide segment of astrip-line.

This allows one to achieve maximum gain factor of this antenna grid.Selection of distance between longitudinal axes of the adjacentstrip-line waveguides to be less than 1/20 wave length in free space ata higher frequency with lateral width of the wide segment of astrip-line results in spurious coupling between the adjacent strip-linewaveguides and reduces a gain factor of the antenna grid. On the otherhand, if the distance is greater than wave length in free space athigher frequency, diffraction lobes, which also reduce gain factor ofthe antenna grid, appear.

It is advisable also that length of every exciting slot of coupling iswithin the range of about 0.8 to 1.0 times the lateral width of thenarrow segment of a strip-line.

This ensures maximum efficiency and, consequently, a gain factor of theantenna grid. On one hand, making the length of every slot be less than0.8 times the lateral width of the narrow segment of a strip-line, doesnot permit one to obtain sufficient coupling between the waveguide-slotradiators on strip-line waveguides with feeding waveguides of thewaveguide-feeder network. On the other hand, making each slot be morethan 1.0 times the lateral width results in spurious radiation from thestrip-line waveguide, which causes losses and reduces the efficiencyfactor of this antenna grid.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully apparent from andescription of the embodiment of the planar slot antenna gridillustrated by the accompanying drawings, wherein:

FIG. 1 is a representation of the planar slot antenna grid, drawn inrectangular isometric projection, according to the invention;

FIG. 2 is a view in the direction indicated by arrow A of FIG. 1.

BEST METHOD OF CARRYING OUT THE INVENTION

Below we describe a planar slot antenna grid employed as an antenna fordirect satellite telecasting systems. This antenna grid contains anumber of waveguide-slot radiators 1 (FIG. 1), each radiatorrepresenting a strip-line waveguide 1a, comprising a dielectricsubstrate 2, the reverse side face of which is covered by metallizedcoating 3 (FIG. 2) serving as a common wide reverse side face 3a of thewaveguide-slot radiators 1. On the outer side face 4 (FIG. 1) of thedielectric substrate 2, there is formed a number of strip lines 5. Eachstrip-line represents a wide outer side face 5a of the waveguide-slotradiator 1 and comprising alternating narrow segments 6 and widesegments 7. In the wide outer side face 5a of the waveguide-slotradiator 1, there are obtained the radiating slots 8. In the commonreverse side face 3a, there are obtained the exciting slots 9 (FIG. 2)of coupling. The common reverse side face 3a and the wide outer sidefaces 5a of the waveguide-slot radiators 1 lie in parallel planes. Onthe metallized coating 3, there is placed a waveguide-feeder network 10comprising a base 11 with rectangular grooves 12 having surfaces havingtogether with the metallized coating surface create channels 12a of thefeeding waveguides 13 and waveguide distributors 14 of power produced inthe form of H-tees. The metallized coating 3 is a wide side face 3b ofthe feeding waveguides 13 and waveguide distributors 14 of power. Length(1) of each exciting slot 9 of coupling lies within the range of about0.8 to 1.0 lateral width W1 (FIG. 1) of the narrow segment 6 of thestrip-line 5. Longitudinal aces O--O of the strip-line waveguides 1a areparallel to each other, and distance d between longitudinal axes O1--O1of the adjacent strip-line waveguides 1a is less than a wave length infree space at higher frequency and more than 1/20 of this wave lengthwith lateral width W2 of the wide segment 7 of the strip-line 5. Aquantity of the waveguide-slot radiators 1, radiating slots 8, feedingwaveguides 13 and waveguide distributors 14 of power is selecteddepending on the required aperture dimension D of the antenna grid andthe range of working frequencies.

The antenna grid operates as follows. A signal received by the antennagrid, through the radiating slot 8, comes to every waveguide-slotradiator 1 and extends along longitudinal axis 01--01 of the strip-linewaveguide 1a as a wave close to an H type. The alternating narrowsegments 6 and wide segments 7 of the strip-line 5 form the wide outerside face 5a of the strip-line waveguide 1a. In the strip-line waveguide1a, the narrow side faces, as elements of construction, are absent.However, the execution of zero boundary conditions for electric field Eyin the planes lying at a distance approximately equal to 1/2 of width W1of the narrow segment 6 of the strip-line 5, in relation to longitudinalaxis 01--01 of the strip-line waveguide 1a, creates conditions forextending the waves of waveguide type in such a line. The waveguide-slot radiator 1 on the strip-line waveguide has the topology ofthe radiating slots 8 and electricity characteristics close to thetopology and electricity characteristics of the waveguide-slot radiatorson the hollow metallic wave guide with a wide side face sizeapproximately equal to width W1 of the narrow segments of thestrip-lines 5, and with a narrow side face size equal to h thickness ofthe dielectric substrate 2 and filled in with dielectric material ofwhich the substrate 2 is produced. The signals from each waveguide-slotradiator 1 on the strip-line waveguides 1a, the radiator representingessentially a resonant or non-resonant waveguide-slot antenna grid on arectangular waveguide filled in with dielectric material, come throughthe exciting slots 9 of coupling to the feeding waveguides 13, andthrough the slots 9, they extend in the waveguide distributors 14 ofpower in which there takes place an in-phase (through the same angle)signal interference and formation of an output signal. The quantity ofthe feeding waveguides 13 and waveguide distributors 14 of power in theantenna grid is determined by the aperture dimensions D and the requiredrange of transmission.

INDUSTRIAL APPLICABILITY

The planar slot antenna grid of the present invention which is utilizedfor the purpose of direct satellite telecasting, at aperture dimensionsof 375×375 mm and thickness of 8 mm, reveals 0.75 efficiency factor and32.9 d.g. gain factor within the range of 10.9 to 11.7 GHz workingfrequencies. The antenna grid of the same construction, havingdimensions of 750×750 mm and thickness of 30 mm, has 0.72 efficiency and38.8 d.g. gain factor within the same range of frequencies.

We claim:
 1. A planar slot antenna grid comprising:a dielectric platehaving a face side and a back side; a plurality of strip lines disposedon said face side of the dielectric plate, each of said strip linesincluding a strip, having a longitudinal axis, and a plurality ofregular stubs disposed symmetrically on both sides of the strip; aplurality of radiating slots provided in said strip; a layer of metalapplied to said back side of the dielectric plate; a plurality ofexciting slots provided in said layer of metal opposite to anappropriate one of said strips and at an angle to the longitudinal axisthereof; a strip line of said plurality of strip lines, with one saidstrip provided with radiating slots, and a section of said layer ofmetal arranged to be disposed opposite to an appropriate one of saidstrip lines on said dielectric plate provided together in each of aplurality of waveguide-slot radiators; and power supply means forsupplying power to the slot antenna grid, said power supply means beingelectrically connected with appropriate exciting slots.
 2. A planar slotantenna grid according to claim 1, wherein said power supply meanscomprises:a base, in which a plurality of channels is provided, disposedon said layer of metal; a second layer of metal applied to a surface ofsaid plurality of channels; and feeding waveguides and waveguidedistributors of power made as H-tees and formed by said surface of saidplurality of channels and said layer of metal applied to the back sideof the dielectric plate; said feeding waveguides being disposed oppositeto said exciting slots.
 3. The planar slot antenna according to claim 1,wherein radiators are parallel, the distance between longitudinal axesof adjacent waveguide-slot radiators being determined from the followinginequality:

    W2+0.05Lb<d<Lb,

wherein Lb is a wavelength, in free space, at an upper frequency of aworking band, W2 is a lateral dimension of the strip line together withtwo of said stubs; and d is the distance between the longitudinal axis.